Thyroid metastasis from breast carcinoma resembling medullary thyroid carcinoma

We are reporting a case of a 42-yr-old female with a history of right breast carcinoma. She was surgically treated (breast quadrantectomy with axillary dissection) and receiving a third cycle of adjuvant chemotherapy when a feeling of a constant pressure in the front of the neck and lack of air occurred. Subsequent work-up revealed a node in the right thyroid lobe with enlarged paratracheal bilateral and right mid and lower jugular lymph nodes. Fine-needle aspiration cytology, repeated within a 20 days window and analyzed by two different cytologists, showed a medullary thyroid carcinoma with a cervical lymph nodes metastasis so the patient underwent total thyroidectomy with selective and paratracheal neck dissection. Histology and immunohistochemistry revealed the specimen to be metastasis of breast carcinoma. During regular follow-up of our patient, eighteen months after initial diagnosis, no new metastases were found. To our best knowledge, this is the first described case of a thyroid metastasis of breast carcinoma that was cytologically misdiagnosed as a medullary thyroid carcinoma.